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* Clean up semaphore EINTR handling after Linux futex docs clarification.Torvald Riegel2015-07-101-30/+7
| | | | | | | The Linux kernel futex documentation now states that since Linux 2.6.22, FUTEX_WAIT does return EINTR only when interrupted by a signal, and not spuriously anymore. We only support more recent kernels, so clean up EINTR handling in the semaphore and update the comments.
* Add and use new glibc-internal futex API.Torvald Riegel2015-07-101-109/+6
| | | | | | | | | | | | | | | | | | | | This adds new functions for futex operations, starting with wait, abstimed_wait, reltimed_wait, wake. They add documentation and error checking according to the current draft of the Linux kernel futex manpage. Waiting with absolute or relative timeouts is split into separate functions. This allows for removing a few cases of code duplication in pthreads code, which uses absolute timeouts; also, it allows us to put platform-specific code to go from an absolute to a relative timeout into the platform-specific futex abstractions.. Futex operations that can be canceled are also split out into separate functions suffixed by "_cancelable". There are separate versions for both Linux and NaCl; while they currently differ only slightly, my expectation is that the separate versions of lowlevellock-futex.h will eventually be merged into futex-internal.h when we get to move the lll_ functions over to the new futex API.
* Make sem_timedwait use FUTEX_CLOCK_REALTIME (bug 18138).Joseph Myers2015-03-181-0/+15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | sem_timedwait converts absolute timeouts to relative to pass them to the futex syscall. (Before the recent reimplementation, on x86_64 it used FUTEX_CLOCK_REALTIME, but not on other architectures.) Correctly implementing POSIX requirements, however, requires use of FUTEX_CLOCK_REALTIME; passing a relative timeout to the kernel does not conform to POSIX. The POSIX specification for sem_timedwait says "The timeout shall be based on the CLOCK_REALTIME clock.". The POSIX specification for clock_settime says "If the value of the CLOCK_REALTIME clock is set via clock_settime(), the new value of the clock shall be used to determine the time of expiration for absolute time services based upon the CLOCK_REALTIME clock. This applies to the time at which armed absolute timers expire. If the absolute time requested at the invocation of such a time service is before the new value of the clock, the time service shall expire immediately as if the clock had reached the requested time normally.". If a relative timeout is passed to the kernel, it is interpreted according to the CLOCK_MONOTONIC clock, and so fails to meet that POSIX requirement in the event of clock changes. This patch makes sem_timedwait use lll_futex_timed_wait_bitset with FUTEX_CLOCK_REALTIME when possible, as done in some other places in NPTL. FUTEX_CLOCK_REALTIME is always available for supported Linux kernel versions; unavailability of lll_futex_timed_wait_bitset is only an issue for hppa (an issue noted in <https://sourceware.org/glibc/wiki/PortStatus>, and fixed by the unreviewed <https://sourceware.org/ml/libc-alpha/2014-12/msg00655.html> that removes the hppa lowlevellock.h completely). In the FUTEX_CLOCK_REALTIME case, the glibc code still needs to check for negative tv_sec and handle that as timeout, because the Linux kernel returns EINVAL not ETIMEDOUT for that case, so resulting in failures of nptl/tst-abstime and nptl/tst-sem13 in the absence of that check. If we're trying to distinguish between Linux-specific and generic-futex NPTL code, I suppose having this in an nptl/ file isn't ideal, but there doesn't seem to be any better place at present. It's not possible to add a testcase for this issue to the testsuite because of the requirement to change the system clock as part of a test (this is a case where testing would require some form of container, with root in that container, and one whose CLOCK_REALTIME is isolated from that of the host; I'm not sure what forms of containers, short of a full virtual machine, provide that clock isolation). Tested for x86_64. Also tested for powerpc with the testcase included in the bug. [BZ #18138] * nptl/sem_waitcommon.c: Include <kernel-features.h>. (futex_abstimed_wait) [__ASSUME_FUTEX_CLOCK_REALTIME && lll_futex_timed_wait_bitset]: Use lll_futex_timed_wait_bitset with FUTEX_CLOCK_REALTIME instead of lll_futex_timed_wait.
* Also use uint64_t in __new_sem_wait_fastH.J. Lu2015-01-231-1/+1
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* Use uint64_t and (uint64_t) 1 for 64-bit intH.J. Lu2015-01-231-5/+5
| | | | | | | | | | | | | | | This patch replaces unsigned long int and 1UL with uint64_t and (uint64_t) 1 to support ILP32 targets like x32. [BZ #17870] * nptl/sem_post.c (__new_sem_post): Replace unsigned long int with uint64_t. * nptl/sem_waitcommon.c (__sem_wait_cleanup): Replace 1UL with (uint64_t) 1. (__new_sem_wait_slow): Replace unsigned long int with uint64_t. Replace 1UL with (uint64_t) 1. * sysdeps/nptl/internaltypes.h (new_sem): Replace unsigned long int with uint64_t.
* Fix semaphore destruction (bug 12674).Carlos O'Donell2015-01-211-0/+467
This commit fixes semaphore destruction by either using 64b atomic operations (where available), or by using two separate fields when only 32b atomic operations are available. In the latter case, we keep a conservative estimate of whether there are any waiting threads in one bit of the field that counts the number of available tokens, thus allowing sem_post to atomically both add a token and determine whether it needs to call futex_wake. See: https://sourceware.org/ml/libc-alpha/2014-12/msg00155.html